Inflatable vane



y 1968 T. s. BRAVERMAN 3,384,183

INFLATABLE VANE Filed May a, 1967 INVENTOR THEODORE S.BRAVERMAN MJMAATTORNEY United States Patent 3,384,183 INFLATABLE VANE Theodore StanleyBraverrnan, 27-21 203rd St, Bayside, Queens, N.Y. 11360 Filed May 8,1967, Ser. No. 636,837 Claims. ((1 170-159) ABSTRACT OF THE DISCLOSUREThe invention relates to an inflatable propeller which is made of rubberor the like. The propeller comprises an elongated body having a fluidexpandable chamber therein and a valve means for introducing fluid intothe fluid expandable chamber. The propeller also includes a hub, saidhub being provided with a pump arrangement therein. A pressure sensitivevalve is connected between the pump arrangement and the fluid expandablechamber for maintaining a pressure gradient between the chamber andatmosphere.

The present invention relates to an inflatable air foil and moreparticularly to an inflatable aeronautical propeller blade or blades orhelicopter and/or movable air foils for airborne vehicles.

Heretofore, it has been known in the prior art of airplane propellersthat dirt in the form of rocks and pebbles are kicked up during anairplanes operation on the ground. It is further of record that debrisin general impinges on the airplane propeller blades not only on takeolfand ground operations but at other times both during and prior to theairplanes becoming airborne.

Those skilled in the art recognize that this occurrence is mostprevalent during the pre-flight check which the pilot makes since he isgenerally parked at one end of the runway and powers his engine to makecertain checks before take-oif. Of course, this impinging of dirt androcks is not limited to the pre-flight check period but is alsofrequently happening during take-01f as well as landing, and taxiing.

Since these rocks and pebbles are kicked up, their most natural point ofimpingement is upon the Leading edges of the propeller blades of anairplane. This problem has recently been aired in the magazine PrivatePilot, the issue dated October, 1966, and again treated in the December,1966, issue of Flighing, and adds to the knowledge of those skilled inthe art. To wit, that the impinging pebble on the leading edge of theair foil causes indentations and holes therein. These indentations,although innocent in appearance, may become the points of a shearingstress in flight, due to the flexing of the air foil, and concentrationof stresses at this point results in the failure of the indented airfoil.

Further, these indentations commonly lead to failures such as fracturingof a portion of the blade which results in vibratory forces caused bythe imbalance of the blade during flight which may result in otherserious complications such as loosing the engine from its mounts andreducing the use of full power of the engine because of the vibratoryforces created.

Various attempts have been made by those skilled in the art to remove ornegate the structural failure created by the nicks or indentations inthe propeller blades but to date there appear to be little or noadequate means of prevention, since none of the major manufacturers ofpropeller blades has brought forth a propeller which overcomes theaforementioned difliculties.

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Since the problem is one that is well recognized by those skilled in theart, it is abundantly clear that to date, until this disclosure, noadequate solution has been found.

It is the object of the present invention therefore to avoid andovercome the difliculties and other objections to prior art devices byproviding a sturdy, resilient and relatively inexpensive inflatablepropeller blade.

It is the primary object of the present invention to provide aninflatable propeller blade using resilient material which will avoid andovercome the prior art failures.

Another object of the present invention is to provide a propeller bladewhich will negate or drastically reduce the susceptibility of therotatable air foil to forces created by the indentations and nicks onthe leading edge of the retating air foils.

A further object of the present invention is to provide an inflatablepropeller blade of relatively resilient material which will decrease theincidents of indentation and nicks in the propeller blade.

Still another object of the present invention in one of its forms is toprovide a rotatable air foil which may be readily mounted and dismountedwhen desired.

A further object of the present invention in one of its forms is toprovide a rotatable air foil of one piece construction.

Yet a further object of the present invention is to provide aninflatable rotatable air foil which will be structurally superior andthe rigidity of the air foil can be controlled as desired.

Yet another object of the present invention is to provide an inflatableair foil which may have its internal pressure controlled so that theinternal pressures of the inflated air foil may be varied in accordancewith the ambient temperatures and pressures thus providing a constantpressure gradient between the internal chamber and atmosphere regardlessof the changes in the atmospheric pressure.

Still another object of the present invention is to provide aninflatable propeller blade to be used in combination with a pump meansfor supplying and maintaining the inflated propeller blade at properrigidity during flight periods.

The principles of the present invention have been achieved by providingan inflatable air foi-l comprising an elongated body member in the wellknown shape of an airplane or helicopter propeller, said body memberbeing composed of a relatively resilient material, at least one fluidexpandable chamber disposed within said body member, connecting meansdisposed on said body member for releasably securing said body member tothe hub of an airplane, valve means in communication with at least oneof said fluid expandable chambers to introduce and remove fluidinternally of said body member and in communication with said fluidexpandable chambers for inflating said propeller blades, and a means forbalancing the propeller blades.

For a better understanding of the present invention reference should behad to the accompanying drawings, wherein like numerals of referenceindicate similar parts throughout the several views and wherein:

FIGURE 1 is a plan view of the air foil,

FIGURE 2 is an end view of the air foil,

FIGURE 3 is a section taken along lines 33 of FIG- URE 1,

FIGURE 4 is a cross sectional view of the hub,

FIGURE 5 is an alternative connecting arrangement of the air foil, and

FIGURE 6 is a cross sectional view of a modified form of the air foil.

Although the principles of the present invention may be broadlyapplicable to air foils of airplanes, helicopters and other airvehicles, it is particularly understood that the present invention isparticularly well adapted for use in conjunction with airplanepropellers and hence it has so been illustrated and will so bedescribed.

With specific reference to the form of the present invention illustratedin the drawings, and referring particularly to FIGURES 1 and 2, aninflatable air foil is indicated generally by the reference numeral 10.

Although the present invention contemplates the use of a form of naturaland/or synthetic rubber as the principal material, it should beparticularly understood that other forms of material exhibiting theproper resiliency, hardness, inflatability and other pertinentproperties may be utilized. For example, certain plastic materials andother forms of synthetic materials such as plastics and nylons as wellas rubber or any combination thereof may be used. Further, it iscontemplated that the particular material utilized as the basicstructural material may be reinforced in a manner such as automobiletires with the use of nylon cord or any other synthetic cord materialwhich will present a reinforced structural material.

For the sake of convenience only, however, the structural materialreferred to in the foregoing description will be rubber.

As shown in FIGURES 1 and 2 the general shape of the air foil,hereinafter referred to as a propeller blade 10, is taken in itsinflated form and mounted upon a hub 12. The propeller blade 10 isprovided with a leading edge 14 and a trailing edge 16. As previouslystated, the inflated propeller blade 10 will take the general overallshape of the well known propeller blade. 7

As shown in FIGURE 2, the aeronautical propeller blade 10 is providedwith an outer wall 18 and thereby creating at least one inner chamber20. However, as shown in FIGURE 2, a pair or more of inner chambers 20may be provided by introducing a reinforcing wall 22 running verticallyor horizontally within the propeller blade 10.

The construction of the preferred embodiment contemplates a pair ofblades 10 integral with each other and having connected between thepair, ring-like hollow member 24 which may be mounted upon the hub ridge26. FIGURE 3 shows a first blade member 28 and a second blade member 30in its inflated form connected to the ring-like hollow member 24.

The outer tips 34, 36 of the aeronautical propeller blades may beprovided with a plurality of holes 38 which may accommodate varioustypes of balancing devices 40 for providing a balance of the first blademember 28 and the second blade member 30.

Further, similar type holes 38 may be provided at the trailing edge 16(not shown) employing similar balancing devices 40 so that the propellerblade or air foil 10 may be balanced.

Other types of balancing means (not shown) may be provided such as ablock of material either at the tip of the blade or trailing edge 16integral with the air foil which may be shaved to accomplish thebalancing thereof. In either case, the balancing means are completelywithin the control of the maintenance of the air vehicle so that variousforms can be utilized and any previously described combination.

At the inner extremities 42, 44 of each first propeller blade member 28and second propeller blade member 30 respectively there may be provideda rigid protrusion 46 around the ring like hollow member 24 to provide ameans .of fixedly mounting the entire aeronautical blade propeller orair foil 10 structure on the hub 12.

It may be seen therefore that when the chambers 20 are filled withfluid, the outer walls 18 will assume the shape of an airplane propellerand maintain the shape as long .4 as the pressure in the respectivechambers 20 is suflicient to keep the outer walls 18 rigid.

It is well known to those skilled in the art that the varioustemperature and altitude changes during the flight of an air vehicle maycause any inflated object to either expand or contract due to thepressure gradient change in the altitude in which the plane is flying.Further, it is necessary that the internal pressure within the chambers26 be maintained such that the propeller blades 10 will remain rigidduring the course of the flight since the lead ing edges 18 and thepropeller blades 10 in general are subjected to extreme stresses andpressures during their normal use in flight. To this end, at least onepump 48 may be provided as shown in FIGURE 4 wherein a constant pumpingaction is maintained so that the fluid pressure within the chambers 29of the propeller blades 28, 30 are maintained such that a relativelyrigid outer wall construction is possible during the flight of the airvehicle.

As shown in FIGURE 4, a convenient location for such a pump arrangement48 may be found in the hub 12 of the air foil itself. It may be seenthat more than one pump 48 may be disposed within the hub 12, as a backup. With the proper passage arrangement and pressure sensitive valvesthe pressure relationship between the atmosphere and the internalchamber 20 of the propeller blade It] may be maintained at a constantpredetermined value.

structurally, as shown in FIGURE 4 at least one pump 48 may be disposedwithin the hub 12 of the air foil 10. To this end the hub 12 may beprovided with a piston bore 50 disposed such that it does not interferewith the operation of the crankshaft 52. A piston head 54 may bereciprocably mounted within the piston bore 50 which Works against theexpansion resilient member 56. The rear 58 of the piston head 54 mayhave connected thereto a piston rod 60 which protrudes rearwardly out ofthe piston bore 50 in the direction of the airplane engine (not shown).At the rearward portion d2 of the piston rod 60 a strike plate 64 may beprovided which when in contact with the cam 66, mounted on the airplaneengine, such that when the hub rotates the striker plate 64 will contactthe cam 66 thereby intermittently forcing the piston head toreciprocate.

Since the piston head 54 works against the resilient member 56, it maybe seen that after the cooperation of the cam 66 and striker plate 64urges the piston head 54 forwardly, the resilient member 50 thereafterforces the piston head 54 rearwardly so that the striker plate 64 is inposition to engage the cam 66 on the following rotation of the hub 12.

As shown in FIGURE 4, a fluid chamber is disposed in the piston bore 50*such that when the piston head 54 is urged forwardly through thecooperation of the cam 66 and striker plate 64 any fluid in the pistonbore 50 will be forced out thereof through a passage 70 and 70A into thechambers 20 within the air foil 10. A passage 72 may be provided in thehub 12 with check valve 74 so that after the fluid in the fluid chambersin the piston bore 50 has been forced into the chambers 20 of the airfoil 10, and the piston head 54 has been urged rearwardly by theresilient member 56, fluid from the atmosphere may enter the bore 50.Further, the check valve 74 will permit the venting to atmosphere offluid when the pressure gradient is at an acceptable level. Manifestly,the check valves 74 will be set to prevent the fluid in the fluidchamber of the bore 50 from escaping through the passage 72.

It should be remembered that the primary purpose of the pump 48 and itsback up 48' is to maintain the proper pressure gradient betweenatmosphere and the internal pressure of the air foil. To this end apressure sensitive valve member (not shown) connected in passages 70,70A must in essence be attuned or set to permit the passage of fluidfrom the fluid chamber of the bore to the chambers 20 in the air foil10, only when the pressure gradient requirements are not satisfied.Valve members of this type are commercially available and any convenientpressure sensitive valve may be used to perform this function. Similarlyit must be recognized that in the event the proper pressure gradient ismaintained, the pumping of the fluid in the fluid chamber of the bore 50will continue, however, instead of the fluid being pumped into thechambers 20 of air foil 10, the fluid may be permitted to be dissipatedto atmosphere through the check valves 74.

A back up pump arrangement 48' is shown in FIG- URE 4 and its operationis identical to that already described in detail.

Since icing is a problem at the leading edge portions of any air vehicleany of the passages venting to atmosphere should be disposed at thoseareas least susceptible to icing.

Alternatively, as shown in FIGURE 6, a molded, one piece air foil 76-may be provided which will accomplish and satisfy the requirementsfulfilled by the preferred embodiment. Structurally, a pair of bladders78 with accompanying air lines 80 may be provided and the one piece airfoil 76 may be molded therearound so that a member of unitaryconstruction will be provided. Although different from the air foil 10,the one piece molded air foil 76 will have certain overall similaritiesto the disclosed preferred air foil 10. For example, the one piecemolded air foil 76 may be provided with a first blade 82 and a secondblade 84 each of which are inflatable or deflatable through theexpansion or collapsing of the bladders 78 simultaneously orindependently. The blades 82, 84- are integrally molded to a connectingplate 86 which may provide for the housing of the pump 48'. Further, theconnecting plate 86 may be provided with a multiplicity of holes 88 sothat the one piece air foil 76 may be releasably secured to the hub 12'.Although only one air chamber is shown in each propeller blade 82, 84,it will be recognized, based on this disclosure, that more than onebladder may be utilized in each propeller blade thereby creating amulti-chamber arrangement similar in nature to that described inconnection with the preferred embodiment.

The one molded piece air foil may utilize the exact same pressure;gradient maintaining apparatus as described in conjunction with thepreferred embodiment since the problems of maintaining the pressuregradient are exactly the same.

A further alternative embodiment may be provided, in that, rather thanhaving two blades integrally made with a connecting means therebetween,individual blades may be mounted into the hub 12. The individual blademay be of similar internal structure of the preferred embodiment,however the means of connection to the hub, of necessity, would beslightly different. It should be noted in this connection however, thatthe valving arrangement previously described would apply to theindividual blades 90 or any of the other embodiments.

It should be noted that in the cases of the alternative embodiments, theessence of the invention is not in any manner departed from but aremerely variations of structure.

Although the invention hereinabove described contemplates the use ofrubber as the basic material for the inflatable air foil, it should beunderstood that other materials and combinations thereof may be used.Recent articles substantially show the advantages of rubber overmaterials such as wood or aluminum in that hard rubber is lighter inweight and in many instances more difficult to damage than either of theother materials above mentioned. Rubber further exhibits the necessaryresiliency to reduce the nicks and pots which may be created by theimpinging of pebbles and the like on the leading edges of the air foils.i

In carrying out the objects of the present invention,

it will be recognized by those skilled in the art that the inventionhereinabove described provides for an inflatable air foil for airplanes,helicopters and other air vehicles which utilize rotating air foils suchthat the serious in flight problems of blade failure is reduced oreliminated.

While in accordance with the patent statutes a perferred and alternativeembodiment are herein shown and described, it is particularly understoodthat the invention should not be limited thereto or thereby.

I claim:

1. An inflatable air foil for air vehicles comprising an elongated body,said elongated body being composed of relatively resilient material, atleast one fluid expandable chamber disposed within said body member,means disposed on said body member for releasably securing said bodymember to the hub of an air vehicle, valve means in communication withat least one of said fluid expandable chambers, at least one pumparrangement disposed in the hub for maintaining said air foil in itsinflated condition, and a pressure sensitive valve connected betweensaid pump arrangement and said fluid expandable chamber for maintaininga pressure gradient between the expandable fluid chamber and atmosphere.

2. An inflatable air foil according to claim 1 wherein said elongatedbody is in the form of a first propeller blade and a second propellerblade, said means disposed on said body member being disposed betweensaid first and second propeller blades.

3. An inflatable air foil according to claim 2 wherein at least onefluid expandable chamber is disposed within each of said first andsecond propeller blades.

4. An inflatable air foil according to claim 3 wherein the hub isprovided with a recessed annular portion, said means disposed on saidbody member connected between said first and second propeller beingconnectable into said recessed annular portion thereby holding saidfirst and second propeller blades on said hub.

5. An inflatable air foil according to claim 4 wherein a plurality ofpassages connect said pump arrangement to said first and secondpropeller blades so that fluid may be pumped thereinto during the flightof the air vehicle.

6. An inflatable air foil according to claim 5 wherein a cam isconnected to the air vehicle so that at each rotation of said hub thepump arrangement will be activated at least once to force air into saidfluid expandable chambers.

7. An inflatable air foil according to claim 6 wherein said pressuresensitive valve is disposed in a passage communicating between said pumparrangement and atmosphere, said passage venting to atmosphere at anarea of said hub which is not susceptible to icing.

8. An inflatable air foil according to claim 7 wherein a second valvearrangement is provided in said hub, said second pump arrangement beingprovided with passages leading therefrom to said fluid expandablechambers, a second pressure sensitive valve disposed in a second passagecommunication between said second pump arrangement and atmosphere, saidsecond passage venting to atmosphere at an area of said hub which is notsusceptible to icing, said second pump arrangement operating alternatelywith said first mentioned pump arrangement.

9. An inflatable air foil according to claim 1 wherein said air foil isof unitary construction, at least one inflatable bladder disposed insaid body member which is to be filled with fluid pumped thereinto, saidunitarily constructed air foil being provided with a connecting means,and being integral with said body member for securing said air foil tosaid hub, sad body member being formed into a first propeller blade anda second propeller blade, said at least one being disposed within eachof said first and second propeller blades, and at least one pumparrangement disposed within said hub being connected to each of said atleast one bladder for maintaining fluid with the bladders.

10. An inflatable air foil according to claim 9 wherein a second pumparrangement is provided and being connectable to said at least onebladder, said second pump arrangement capable of operating alternatelywith said first mentioned pump arrangement.

References Cited UNITED STATES PATENTS EVERETTE A. POWELL, J R., PrimaryExaminer.

